The invention relates to a strut for a wheel suspension of the Mac Pherson type, comprising a shock absorber with a body and a rod. The rod is surrounded by a coil spring. The coil spring is mounted preloaded between a bottom seat of a lower spring retainer secured to the shock absorber body and an upper seat of an upper spring retainer through which the shock absorber rod passes. The shock absorber body is mounted securely to a hub carrier defining an axis of rotation of the wheel.
Document EP-0 780 250 A2 describes a precise adjustment of a Mac Pherson suspension strut, using adjusting means arranged on the strut and preferably employing an appropriate measurement bench. To obtain correct operation of the strut, the shear force applied to the shock absorber rod has to be precisely controlled. To achieve this, it is known practice for the axis of the spring to be inclined with respect to the axis of the shock absorber rod with an inclination that is calculated to minimize the shear force on the shock absorber rod. However, it is also known that the resultant of the forces exerted by the spring is liable to exert a moment about the pivot axis, which moment has to be well controlled.
One object of the invention is to perfect the state of the art described in document EP-0 780 250 A2 by proposing a new strut allowing quick and precise adjustment and which is simple and economical to manufacture.
The subject of the invention is a strut for a wheel suspension of the Mac Pherson type, comprising a shock absorber with a body and a rod; said rod being surrounded by a coil spring; said coil spring being mounted between a lower spring retainer secured to the shock absorber body and an upper spring retainer through which the shock absorber rod passes; said shock absorber body being mounted secured to a hub carrier defining an axis of rotation of the wheel, characterized in that the strut comprises means capable of immobilizing the first turn of the spring on and with respect to the lower spring retainer in various predetermined positions on the lower spring retainer.
According to other features of the invention:
The spring has one end extending transversely to a direction of translation defined by the various predetermined positions and has a part which is roughly straight and parallel to the direction of translation.
According to a first alternative form of the invention, the said end of the spring extends transversely to the direction of translation and has an indexing configuration.
In a first embodiment of this first alternative form, this indexing configuration involves at least one orifice through which a mechanical means of connection to the lower spring retainer can pass.
In a second embodiment of this first alternative form, this indexing configuration involves at least one curved end which can be inserted in an indexing orifice chosen from a number of orifices made in the lower spring retainer.
According to a second alternative form of the invention, corresponding to a third embodiment, the said end of the spring extends transversely to the direction of translation and can be secured to the lower spring retainer by a means at least partially surrounding said end. This means at least partially surrounding said end of the spring is advantageously configured as a collar or a curved tab. This collar or curved-tab configuration has a means of attachment by a mechanical coupling means to the lower spring retainer.
In both alternative forms of the invention, the mechanical means of coupling to the lower spring retainer is preferably a replaceable means and can be of the screw, pin, bolt or similar type.
As a preference, said straight part parallel to the direction of translation is parallel to the direction of forward travel of a vehicle for which the strut is intended.